Floating devices such as emergency radio beacons or life rafts are normally secured to a watercraft by tethers when not in use. As is well known, such life rafts are designed for use by the crew of said watercraft in an emergency. However, when the crew finds itself in a rapid sinking situation caused by, for example, when the structural integrity of the watercraft is seriously compromised via a collision with another vessel or a reef, there may not be enough time to release all of the floating emergency equipment on a vessel. Other rapid sinking scenarios include, but are not limited to, explosions, fire, storms and the like. In such situations, the crew may find itself in the water with needed life rafts and emergency radio beacons still attached to the now submerged vessel.
There have been a number of mechanisms designed to alleviate this problem. For example, U.S. Pat. No. 6,224,442 entitled “Release Unit” issued on May 1, 2001 to Simpson et al. discloses a device for releasing a link between a first object and a second object. The device comprises a body having a holding means for securing the body to the link; a releasing means for releasing the link; a pyrotechnic composition for actuating the releasing means; an igniting means for igniting the pyrotechnic composition, the igniting means being actuated by an increase in ambient pressure; and a pressure sensing means for detecting a change in ambient pressure. In one embodiment, the device can include a sliding blade actuatable by a pyrotechnic composition  that is ignited by an electrical stimulus activated by an increase in ambient pressure, and the link may be, for example, a cable securing an emergency radio beacon to a water craft. If the water craft becomes submerged, and the device is thereby exposed to an increase in ambient pressure, the electrical stimulus will be activated to ignite the pyrotechnic composition which, in turn, will actuate the sliding blade which then operates to cut the securing cable and release the EPIRB from the water craft. However, note the use of electrical stimulus to initiate the process.
U.S. Pat. No. 5,365,873 entitled “Hydrostatic Pressure Sensors” which issued on Nov. 22, 1994 to Wigram shows a hydrostatic pressure release for releasing a lift raft or the like when a ship sinks. A flexible diaphragm seals a chamber on one side and is exposed externally on its opposite side. A ceramic vent plug is mounted on the diaphragm so that it is protected within the casing of the device. The diaphragm has a resilient plate with an integral sleeve that projects through the collar in a rigid disc mounted on the plate. The plug is retained within the sleeve, in the collar. A rod projecting from the diaphragm extends into one end of an aperture in a slider and locks it in position. When the device is submerged, the diaphragm is deflected and pulls the rod out of the aperture allowing the slider to be released. A button on the slider extends into the other end of the aperture so that when it is depressed it pushes the rod out of the aperture and releases the slider. 
U.S. Pat. No. 5,177,317 entitled “Cable Cutter Assembly” which issued on Jan. 5, 1993 to Walker et al. shows an explosive-type cable cutter assembly which includes a breech housing having a central passageway formed in it and a first slot extending from the exterior surface of the breech housing and opening into the passageway and a second slot extending from the exterior surface of the breech housing and opening into the passageway. The slots are each elongated in the direction of the central axis of the breech and each include a forward most edge and a rearward most edge. The cable cutting assembly also includes a threadable plug with an impact wall positioned forward of the slots and radial ports extending from the exterior surface of the breech housing into the passageway between the impact wall and the slots.
U.S. Pat. No. 3,885,484 entitled “Explosively Actuated Compressed Disc Line Cutter” which issued on May 27, 1975 to Sturgis provides a cutting tool for use in severing lines and cables, especially those which are constructed from multi-filament, low denier polymer resins. As explosively activated piston drives a compressed disc through a segment of a multi-filament cable or line, thereby shearing a small segment thereof.
None of the known prior art disclose the combination set forth herein.